1. Field of the Invention
The invention relates to a device for exposure of a continuous workpiece with a great length (hereinafter called a "strip-like workpiece"), such as a film of organic compound, lightweight metal, or the like. The invention relates especially to an exposure device for a strip-like workpiece which is used for exposure of a mask pattern onto a strip-like workpiece and for similar purposes.
2. Description of Related Art
Exposure of a strip-like workpiece, such as a film of organic compound, lightweight metal or the like is performed by the workpiece being unrolled from the rolled state, exposed and wound again onto a reel.
To transport the strip-like workpieces which are used for the above described exposure device, generally a tensile force is always applied to the workpiece between a takeoff reel and a take-up reel in order to ensure the stability and positioning accuracy of the workpiece during the workpiece transport and to correct bulging and waviness of the workpiece.
FIG. 6 is a schematic of a conventional example of the above described exposure device for a strip-like workpiece. In the figure, a takeoff reel part 10 is shown in which a takeoff reel 1, a spacer take-up reel 1a and a guide roller R1 are located. Furthermore, a strip-like workpiece Wb is conventionally located on a spacer S which is wound in the manner of a roll around the takeoff reel 1. When the strip-like workpiece Wb is unrolled from the takeoff reel 1, the spacer S is wound up by the spacer take-up reel 1a.
The strip-like workpiece Wb is relatively thick (t.gtoreq.150 microns, often t=250 microns). For example, a workpiece is used which was produced by a resin film being coated with a copper foil (conventionally thicker than the resin film). Therefore, there are strip-like workpieces Wb which have bulges in the direction of their width.
To transport a strip-like workpiece, for example, the process described in published Japanese Patent Application HEI 3-19249 is used in which the peripheral edge of the strip-like workpiece Wb is clamped using a grip feeding device described below, is pulled by a preset amount, and the strip-like workpiece Wb is transported by a predetermined amount (hereinafter this transport process is called a "grip feeding method").
The grip feeding method is effective when a strip-like workpiece which is thick and has a bulge in the direction of the width is transported without contact with the area to be exposed. In this method, the two edges of the workpiece are gripped and the workpiece is pulled in the fixed state. The workpiece therefore does not fall out of the transport means even if a workpiece with a bulge is transported at high speed.
The strip-like workpiece Wb which has been pulled off the takeoff reel 1 by a grip feeding device 11 is supplied to an exposure part 3 which has a workpiece carrier WS and the like, via the guide roller R1, an edge sensor S1 which determines the edge position of the strip-like workpiece, and a guide roller R2. If a predetermined area of the strip-like workpiece reaches the exposure part 3, transport of the strip-like workpiece Wb is stopped and the strip-like workpiece is exposed.
The strip-like workpiece Wb which is exposed in the exposure part 3 is wound up via guide rollers R3 and R4 by a take-up reel 2. When the strip-like workpiece Wb is wound up, a spacer 5 is supplied from a spacer takeoff reel 2a and the already exposed, strip-like workpiece Wb, together with the spacer S, is wound up by the take-up reel 2.
Here, it is desirable to always apply a tensile force to the strip-like workpiece Wb to prevent waviness and folds from forming in the strip-like workpiece Wb. Therefore, the takeoff reel 1 is always exposed to a force which is opposite to the transport direction of the strip-like workpiece Wb (in FIG. 6, to the right), so that, between the takeoff reel 1 and the take-up reel 2, the strip-like workpiece Wb is always exposed to a tensile force during its transport and also when stopped.
The take-up reel 2 is likewise always subjected to a force and turned in a direction in which the strip-like workpiece Wb is wound up. Between the takeoff reel 1 and the take-up reel 2, therefore, the strip-like workpiece Wb is always subjected to a tensile force.
In the above described exposure device for a strip-like workpiece, the strip-like workpiece Wb is transported in the manner described below, exposed and subjected to serpentine correction:
(1) Transport and Exposure of the Strip-like Workpiece Wb by the Grip Feeding Device
The peripheral edge of the strip-like workpiece Wb is clamped by the grip feeding device and the strip-like workpiece Wb is transported by a stipulated amount. FIG. 7 shows an enlarged view of the grip feeding device which is shown in FIG. 6. As is shown in the drawings, the grip feeding device 11 has a feed grip part 12 which holds the edge of the strip-like workpiece Wb, and a feed grip drive part 13 which moves the feed grip part 12 by a predetermined amount.
The feed grip drive part 13, for example, has a ball-circulating spindle 13b which is turned by a feed motor 13a and a drive belt 13c, as is shown in the drawing. The motor 13a turns the ball-circulating spindle 13b, and the feed grip part 12 which engages the ball-circulating spindle 13b moves in the direction of the arrow in the representation. FIG. 8 is a schematic of the arrangement of a specific example of the above described grip feeding device 11, a workpiece carrier WS, which is viewed here from the transport direction, being shown in cross section, and the grip feeding device 11 also being shown. In the figure, a feed grip part 12 is shown only on one side, although on the other side there is also a feed grip part 12 with the same arrangement. The two edges of the strip-like workpiece Wb are held and the strip-like workpiece Wb is transported in this state. As is shown in the drawings, the feed grip part 12 engages the above described ball-circulating spindle 13b and is installed in a holding frame 12b for a grip device which is located on both sides of a movement part 12a which is guided using a feed guide 13d which moves forward and backward in the drawing. The edge area of the strip-like workpiece Wb is clamped from the bottom and top by a grip part Gr1 of a top component 12c and a grip part Gr2 of a bottom component 12d.
A guide shaft 12e, which is slidably installed in the holding frame 12b, is installed in the bottom component 12d. Furthermore, in the holding frame 12b, there is a first pneumatic piston 12f with a drive rod which has been installed in the bottom component 12d. When the first pneumatic piston 12f is being driven, therefore, the bottom component 12d is moved up.
The top component 12c is attached via a shaft 12g to the bottom component 12d and turns around the shaft 12g. On the side opposite the grip parts Gr1, Gr2 of the top component 12c and the bottom component 12d there is a spring 12h by which the top component 12c and the bottom component 12d are prestressed in a direction in which the grip parts Gr1 and Gr2 open.
In the bottom component 12d, there is a second pneumatic piston 12i, with a drive rod which penetrates the bottom component 12d and projects from it, and with a tip which borders the top component 12c. When the second pneumatic piston 12i is being driven, therefore the top component 12c turns around the shaft 12g and the grip parts Gr1 and Gr2 close.
On the other hand, the workpiece carrier WS is provided with vacuum suction openings O, as is shown in the drawings. When the strip-like workpiece Wb is exposed, a vacuum is applied by a vacuum part VP and the strip-like workpiece Wb is attached by suction through the vacuum suction openings O.
The strip-like workpiece Wb is clamped and is transported by the feed grip device 12 as follows:
Proceeding from the state which is shown in FIG. 9(a), the bottom component 12d is lifted by the first pneumatic piston 12f. As is shown in FIG. 9(b), the grip part Gr2 of the bottom component 12d comes into contact with the back of the strip-like workpiece Wb. The second pneumatic piston 12i is lifted. The grip part Gr1 of the top component 12c which clamps the strip-like workpiece Wb is lowered and clamps the strip-like workpiece Wb.
When the feed grip device 12 is holding the strip-like workpiece Wb, the ball-circulating spindle 13b of the feed grip drive part 13 turns and the feed grip device 12 moves downstream of the transport direction by a predetermined amount.
In this way, the strip-like workpiece Wb is transported by a set amount and the area of the strip-like workpiece Wb to be exposed next is transported to the exposure part 3.
During transport of the strip-like workpiece Wb, the workpiece carrier WS is removed underneath the transport plane. This prevents the back of the strip-like workpiece Wb from coming into contact with the workpiece carrier WS and being damaged. The danger of damage of the back of the strip-like workpiece Wb by contact with the workpiece carrier WS is furthermore prevented by air flowing out of the vacuum suction openings O of the workpiece carrier WS which are arranged for attachment of the strip-like workpiece (see FIG. 8) during transport of the strip-like workpiece Wb.
When the strip-like workpiece Wb has moved the predetermined amount and the area of the strip-like workpiece Wb to be exposed reaches the exposure part 3, movement of the strip-like workpiece Wb is stopped. The workpiece carrier WS which has been removed downward is lifted by a workpiece carrier drive part WSD (FIG. 6) as far as the transport plane. A vacuum is applied to the workpiece carrier WS by the above described vacuum part VP. The strip-like workpiece Wb is held stationary by vacuum suction on the surface of the workpiece carrier WS.
If, in doing so, the strip-like workpiece Wb remains clamped in the feed grip part 12, it is suctioned by the workpiece carrier WS in a state in which transport tensile force is applied to the strip-like workpiece Wb by the feed grip device 12. Also in the case in which the feed grip device 12 has released the hold of the strip-like workpiece Wb, the latter is suctioned by the workpiece carrier WS in a state in which it is subjected to the tensile force which forms between the takeoff reel 1 and the take-up reel 2.
When the strip-like workpiece Wb is attached to the workpiece carrier WS by suction, the second pneumatic piston 12i is pulled back. The top component 12c of the feed grip parts 12 turns, and the grip parts Gr1 and Gr2 release the strip-like workpiece Wb (state as shown in FIG. 9(b)). Furthermore, the first pneumatic piston 12f is pulled back and the bottom component 12d is lowered (state as shown in FIG. 9(a)). Then the feed grip part 12 is moved by the feed grip drive part 13 upstream of the transport direction and returns to the original position.
On the other hand, in the exposure part 3, a mask carrier drive part MSD moves a mask M, and positioning of the mask M to the workpiece and exposure are performed.
After completion of exposure, the two sides of the strip-like workpiece Wb are clamped by the feed grip parts 12. Furthermore, the vacuum attachment of the strip-like workpiece Wb is released by the workpiece carrier WS and the workpiece carrier WS is removed down. Next, the two edges of the strip-like workpiece Wb are held by the feed grip parts 12 which have been returned to the original position which is upstream of the transport direction, as was described above. The respective feed grip part 12 is moved downstream of the transport direction and the strip-like workpiece Wb is transported such that an area of the strip-like workpiece Wb which is to be exposed next reaches the exposure part 3.
(2) Serpentine Correction
When the strip-like workpiece Wb is being continuously transported, there are cases in which the strip-like workpiece Wb in the exposure part 3 in the direction of the width of the strip-like workpiece Wb (in the direction which is perpendicular to the feed direction of the strip-like workpiece Wb) has a position deviation. This must be corrected and the correct position of the strip-like workpiece Wb in the exposure part must be ensured. In doing so, a deviation of the strip-like workpiece Wb in the direction of the width is called the "serpentine" of the strip-like workpiece Wb. Correction of the serpentine of the strip-like workpiece Wb is called "serpentine correction."
In the above described case of a device in which the entire strip-like workpiece Wb is always subjected to a tensile force, the serpentine of the strip-like workpiece Wb is determined and corrected in the manner described below:
As is shown in FIG. 10, in the exposure part 3 at a stipulated position upstream of the workpiece transport direction there is an edge sensor S1 by which the edge position of the strip-like workpiece Wb is determined. The output of the edge sensor S1 is sent via a control member 31 to a takeoff reel drive device 32 and to an actuator 33. If during transport the edge sensor S1 determines a serpentine of the strip-like workpiece Wb, the control member 31, via the device 32 and by the actuator 33, moves the entire takeoff reel part 10 in the direction of the width of the strip-like workpiece Wb and corrects the serpentine.
An edge sensor as shown in FIG. 11(a) and (b) can be used as the edge sensor S1. As is shown in FIG. 11(a), an edge sensor can be used in which there are two pairs of photosensors S11 and S12 next to one another on the outside and inside of the strip-like workpiece Wb, the photosensor S11 being comprised of an emission element L11 and a light detection element PT1 and the photosensor S12 being comprised of an emission element L12 and a light detection element PT2.
Alternatively, a linear sensor S13 which is shown in FIG. 11(b) can be used which is composed of an emission element L13 and a line sensor LS1, such as a CCD or the like, which is located perpendicularly to the transport direction of the workpiece.
When using the sensor which is shown in FIG. 11(a), the edge position of the strip-like workpiece Wb is determined by a combination of ON and OFF of the photosensors S11 and S12. When using the sensor which is shown in FIG. 11(b), the edge position of the strip-like workpiece Wb is determined at a position at which the light is incident on the line sensor LS1.
As was described above, the workpiece in a conventional device in a state in which the strip-like workpiece Wb is exposed to a tensile force is held stationary by the workpiece carrier WS and exposed. If the strip-like workpiece Wb is, for example, a thin film of organic compound, the strip-like workpiece Wb is therefore exposed in a stretched state. When it is removed from the exposure device, the strip-like workpiece Wb is not exposed to a tensile force, by which the disadvantages arise that the strip-like workpiece Wb shrinks and the exposure accuracy changes.
When exposure is performed in a state as shown in FIG. 12(a) in which the tensile force is exerted and then the tensile force is removed, the strip-like workpiece Wb shrinks and the position of the exposure pattern deviates, as is shown in FIG. 12(b). In this way, the exposure accuracy can no longer be guaranteed.
Recently, the above described disadvantages were considered more and more often to be especially problematical due to the increase need for exposure accuracy, such as with miniaturization of the exposure pattern or the like.